Smart GaNBased Inverters for Gridtied Energy Storage Systems

Battery storage systems are the backbone of the future grids. These systems provide distributed energy storage capabilities for smoothing the load profile and coping with generation and load power fluctuations. By incorporating these resources, voltage stability and overall reliability of the grid will improve. A challenge in the utilization of battery storage systems is the design and manufacturing of high efficiency high power density bidirectional inverters to interface between batteries and the utility grid. Traditional Silicon based inverters do not offer high efficiencies and suffer from larger real estate requirements. Recent commercialization of low cost Gallium Nitride (GaN) semiconductors has opened up an opportunity to manufacture high efficiency inverters that can operate at higher switching frequencies and demand smaller filtering elements. InnoCit’s technical approach is to utilize modular stacks of printed circuit boards (PCB) as the core of its GaNinverters. InnoCit has devised a modular 10 kVA diodeclamped multilevel GaNinverter to form a rack based 100kVA inverter. By using a multilevel topology, InnoCit is able to utilize the commercially available low voltage GaN switches. Using a modular rack based design on PCBs, InnoCit has introduced an innovated automated manufacturing method to eliminate the traditional dc bus structures and wiring. As a result, InnoCit has significantly reduced its manufacturing and labor cost and will offer a 20% lower price tag compared to the competing products. Also, InnoCit’s solution reduces the size by 74%. During the Phase I project, InnoCit performed a preliminary market analysis and developed estimates of the market growth. Also, the team interviewed several potential customers. On the technical side, the team performed comprehensive simulations and finalized its converter topology. A gate driver circuitry was designed and developed for GaN switches that was commercialized and is now available for purchase on InnoCit’s website as well as Amazon. Lastly, a TRL4 prototype of the proposed battery inverter was developed and tested. During this Phase II project, InnoCit LLC will revise its TRL4 GaN inverter prototype to a TRL7 prototype ready for certification testing. To this end, the team will finalize the design of the circuit boards, design a rack drawer system to use with modular 7.5kW units, and will design a rack cabinet to house ten GaN inverter modules to form a 75kW inverter. Tasks include CAD modeling, FEM thermal analysis, programing, electrical measurements for EMI compliance, and isolation voltage analysis based on UL requirements. Additionally, InnoCit GaN inverter will be tuned to support hybrid battery racks with multiple chemistries and to offer a CEC efficiency of 89.5%. Also, a U.S. manufacturing and commercialization plan will be developed. Lastly, field tests with demonstrations to potential customers and early market adopters will be executed. InnoCit is aiming to commercialize its full GaN inverter system by 2018. This project helps DOE to reach its SunShot goals by enabling high penetration of intermittent resources though the use of battery systems for compensation of power fluctuations. Due to its lower cost, public will benefit from a reduced capital investment requirements and larger return on investment rates. Keywords: Gallium Nitride, Wide Bandgap, Battery Inverter, Low Cost, GaN, High Efficiency, Hybridchemistry